1. Field of the Invention
The present invention relates to an optical disk drive for optically accessing an optical disk on which information is recorded at least optically, in particular to a drive mechanism for a carriage driver provided for the optical disk drive.
2. Related Arts
In an optical disk drive, a carriage is guided along guide rails on a base to move track crossing direction of the optical disk for guiding a light beam, which is irradiated from a light source, such as a semiconductor laser, to a track on the optical disk through a lens mounted on the carriage. The carriage is urged to the guide rails by its own weight, and slides along the guide rails.
However, if a force exceeding the urging force is applied to the carriage by vibrations, the carriage may be displaced with a tracking-off state and a focusing-off state. In order to resolve this problem, various methods have been proposed for increasing the urging force to the carriage against the guide rails.
For example, Japanese Unexamined Patent Publication No. Hei 6-103586 discloses a method for increasing the urging force, as is shown in FIG. 6A, by an attractive force between a base made of magnetic material and a magnet attached to the bottom of the carriage.
Japanese Unexamined Patent Publication No. Hei 2-273383 and Hei 3-5971 discloses a method for increasing the urging force, as is shown in FIG. 6B, by an attractive force between a magnet mounted on the carriage and guide rails made of magnetic material.
Japanese Unexamined Patent Publication No. Hei 4-82059 discloses a method for increasing the urging force by an attractive force between a magnet constituting a magnetic circuit for driving the carriage and magnetic material included in the carriage.
Japanese Unexamined Patent Publication No. Hei 7-66514 discloses a method for increasing the urging force by attractive force between a magnet constituting a magnetic circuit mounted on the carriage and guide rails made of magnetic material.
Instead of increasing the urging force by using the attractive force of the magnets, the urging force to the carriage against the guide rails may be so adjusted as to weaken the urging force by using a repulsive force of the magnets to reduce friction by sliding of the carriage. As a result, a moving speed of the carriage can be increased and the power required to drive the carriage can be reduced.
As is described above, in accordance with the design conditions for the optical disk drive, the urging force to the carriage against guide rails must be adjusted.
However, as is disclosed in the prior art, a special mechanism is required to adjust the urging force: a new component (e.g., a magnet) must be added, or a special material must be used for a component (e.g., guide rails and/or a carriage must be made of a magnetic material). Those cause manufacturing costs and the weight of the optical disk drive to increase.
It is, therefore, one objective of the present invention to provide an optical disk drive which can adjust the urging force to the carriage against the guide rails without a special mechanism being required.
To achieve the above objective, according to a first aspect of the present invention, there is provided 1. An optical disk drive for accessing an optical disk on which information is recorded at least optically by irradiating a light beam to the optical disk, comprising:
a carriage mounting a lens for guiding the light beam to the optical disk and moving in a track crossing direction of the optical disk;
a base having guide rails for guiding said carriage in the track crossing direction;
a first magnet attached to said base;
a first coil generating a force to drive said carriage along said guide rails by the magnetic field of said first magnet;
a second magnet attached to said carriage with shifting perpendicularly relative to said first magnet; and
a second coil generating a force to drive the lens in a light axial direction by the magnetic field of said second magnet.
With the first arrangement, since the force having a perpendicular element is generated between the first magnet and the second magnet, the urging force to the carriage against the guide rails can be adjusted.
The first magnet and the second magnet are so arranged as to generate a perpendicular attractive force. Thus, the urging force can be increased and vibration of the carriage can be restricted.
Further, the first magnet and the second magnet are so arranged as to generate a perpendicular repulsive force. Thus, the urging force can be reduced, so that the speed at which the carriage is moved is increased, and the power consumed to drive the carriage is reduced.
To achieve the above object, according to a second aspect of the present invention, there is provided an optical disk drive for accessing an optical disk on which information is recorded at least optically by irradiating a light beam to the optical disk, comprising:
a carriage mounting a lens for guiding the light beam to the optical disk and moving in a track crossing direction of the optical disk;
a base having guide rails for guiding said carriage in the track crossing direction;
a first magnet attached to said base;
a first coil generating a force to drive said carriage along said guide rails by the magnetic field of said first magnet;
a second magnet attached to said carriage with shifting perpendicularly relative to said first magnet; and
a second coil generating a force to drive the lens in a light axial direction by the magnetic field of said second magnet,
wherein one of the polarities of said first and second magnets is perpendicularly symmetrical in the center portion and the other polarity is perpendicularly asymmetrical.
With the second arrangement, since the force having a perpendicular element is generated between the first and the second magnets, the urging force to the carriage against the guide rails can be adjusted.